Photographic emulsions sensitized with quaternary dithiocarbamates



U ited tews Patent O ce 2,931,090 Patented May 17, 1960 flinorocnArmcEMULSIONS SENSITIZED WITH QUATERNARY DITHIQCARBAMATES Kenneth C. Kennardand DonaldM. Burness, Rochester,

N.Y., assiguors to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey No Drawing. Application May 19, 1958 Serial No. 135,921

4 Claims. (Cl. 95-107 -This application relates to photography andparticularly to sensitizing photographic emulsions.

It is well known that silver halide emulsions may be chemicallysensitized with a variety of materials in order to increase the speedand generally'the gamma of the emulsion, as opposed to opticalsensitization'in-which the optical range of sensitivity is increased.Chemical sensitization usually results either-from theforrnation ofsilver sulfide on the surface of the silver halide "crystal, thusincreasing sensitivity, or from, the formation of small amount'of silverfromthe reduction of silver halide Other classes'ofcomp'ofunds, such ascertain ethylene oxide condensation products and certain cationicsurface-active salts increase sensitivity of silver halides 'withoutapparently entering into chemical combinationwith the silver halide. p 1

' Carroll US. Patent 2,271,623, Carroll and Allen U.S. Patent 2,288,226and Carroll and Spence U.S. Patent 2,334,864 describe the chemicalsensitiz'a'tionof silver halide emulsions with quaternary ammoniumcompounds.

-We'hav'e now found that the light sensitivity of silver.

halide emulsions, with or without optical sensitizing dyes, may befurther increased by incorporating, in the emulsions certain quaternarydithiocarbamates. These compounds are incorporated-in the emulsion afterdigestion but-before coating and exposure. .Thecompounds which Wepropose to use havethe following-structure:

in which R represents an alkyl or substituted alkyl group such asmethyl, ethyl; propyl,hydroxyethyl, sulfoalkyl or carboiiyalkyl, Rrepresents a lower alk'yl group such as' inethyl or ethyl, x is 1, 2or'3,' andXisan anion or acid radical, for example, halide, ptoluenes'ulfonate, a1-

y ateor perchlorate. f1;-

The following specific compoundsmay be employed as 'sensitizersaccording to our invention.

goinpsor.

n- 9 1 CBFzSCN( CHa)z censor- 1. i The preparation of silver halideemulsions involves V (4) V era-N cmnsiimonm (nor (in s u em-Qmmnsoummn(6) OHil-IQ l OHzSON( s)n The emulsions may be chemically sensitized byany of the accepted procedures, for example, by digestion with naturallyactive gelatin or the addition of sulfur compounds such asthosedescribed in Sheppard U.S. Patents 1,574,944 and 1,623,499 and Sheppardand Brigham U.S. Patent 2,410,689.

The emulsions may also be treatedwith salts ofthe noble metals such asruthenium, rhodium, palladium,

iridium and platinum, an of which belong to group VIII of theperiodic-table of elements and have an atomic? weight greater'th'an 100. Representative compounds are" M ammonium" chloropalladate, potassiumchloroplatinat'e j and sodium chloropalladite, which'are used forsensitizing in amounts below that which produces any substantial foginhibition, as described in Smith and Trivelli U.S. Patent 2,448,060,and as anti-foggants in higher amounts, as described in Trivelli andSmith U.S. Patents 2,566,245

' and 2,566,263. r

The emulsions may'also be chemically sensitized with goldsalts as,described in Waller and Dodd U.S. Patent 2,399,083 or stabilized withgoldsalts as described in Damschroder U.S. Patent 2,597,856 and Yutzyand Leer makers U.S. Patent 2,597,915. 3 Suitable compounds arepotassium chloroau'rite, potassium .aurithiocyanate, potas:

sium' chloroaurate, auric trichloride and Z-aurosulfobenzothiazolemethochloride. i a p 1 The emulsions may also be chemicallysensitizedwith reducing agents such as' stannous saltsl (Carroll U.S. Pat.- ent-2,487,850), 'poly'amine's such asdiethylene triamine v (Lowe and JonesU.S. Patent 2,518,698), polyaminesg such as spermine (Lowe and Allen US.:Patent 2,521,-" 925), or bis-(p-aminoethyl) sulfide anditswater-soluble salts (Lowe and Jones U.S. Patent 2,521,926).

The emulsions may also be stabilized with the mercury compounds ofAllen, Byers and Murray U.S. application Serial No. 319,611, Carroll andMurray U.S. application Serial No. 319,612 and Leubner and Murray U.S.

it application Serial No. 319,613, all filed'November 8,

1952, now U.S. Patents 2,728,663,'2,728,664 and 2,728,:

665 respectively, granted December 27, 5

Other stabilizing agents may be-added to the emulsions containing thequaternary ammonium' compounds and polyalkylene oxides such as cadmiumchloride, cadmium nitrate, cobalt nitrate, manganese chloride, manganesesulfate, zinc chloride, zinc nitrate and zinc sulfate.

The emulsions sensitized with quaternary dithiocarbamates may beadditionally sensitized with alkylene oxide polymers or derivatives ofalkylene oxides.

The alkylene oxide polymers used to sensitize the emulsions may be ofvarious types. The alkylene oxides from which the polymers are derivedcontain from 2 to 4 carbon atoms, e.g., ethylene oxide, propylene oxideand butylene oxide. The preparation of polymers from these compounds isdescribed in Ellis, The Chemistry of Synthetic Resins (1935), pages 990to 994. These compounds are also referred to as polyalkylene glycols andtheir use as sensitizers for silver halide emulsions is described in US.Patents 2,423,549 and 2,441,389. The alkylene oxide derivatives may beprepared by condensing an organic compound containing an active hydrogenatom with an alkylene oxide polymer, or by condensing the activehydrogen compound with the alkylene oxide during the polymerization ofthe latter material.

Various derivatives of alkylene oxides may also be used to sensitizethe'emulsions, e.g., condensation products of alkylene oxide withorganic compounds containing an active hydrogen atom. Examples of activehydrogen organic compounds, i.e., compounds in which a hydrogen atom maybe replaced by reaction of the compound with metallic sodium,methylmagnesium iodide, etc., include alcohols, amines, mercaptans,acids, amides, hydrocarbons such as acetylene, and compounds having theactive hydrogen in a methylene group such as dibenzoylmethane. Morespecifically, we may employ condensation products of alkylene oxide withglycols such as those having from 8 to 18 carbon atoms as described inUS. Patent 2,240,472 and British Patent 443,559 as well as condensationproducts of alkylene oxides with aliphatic alcohols, condensationproducts of alkylene oxides with aliphatic acids, e.g., lauric acid andglycine, condensation products of alkylene oxides with aliphatic aminesorv amides, e.g., glycine and lauryl amide, and

Our invention is further illustrated by reference to the followingexample:

EXAMPLE To portions of an optically sensitized gelatino-silverbromoiodide emulsion containing about mol of silver halide per liter,which had been digested with a sulfur compound such as disclosed inSheppard U.S. Patent 1,574,944, and a gold'compound such as disclosed inUS. Patent 2,399,083, and stabilized with an azaindene, were added theamounts of Compound 5 shown in the following table:

Amount Relative Compound per mole Speed Gamma Fog of AgBrI Control -1115 1.22 12 Compound 5 75 166 1. 03 16 Compound 5 3.0 174 96 18 Theemulsions Were coated on film support in the conventional manner,exposed on an Eastman-type l-b sensitometer and processed for 5 minutesin-DK-SO-developer having the following composition with the resultsshown in the table, speed being shown as a relative speed in each casewith the control being designated Developer DK50: GramsN-methyl-p-aminophenol sulfate 2.5 Hydroquinone 2.5 Sodium sulfite,desiccated 30.0 Sodium metaborate -5. 10.0 Potassium bromide 0.5

Water to make 1 liter. 7

The compounds'which we use maybe prepared as follows:

Compound 5 'y-3-CHLOROPROPYLPYRIDINE tracted with 150 ml. of chloroform,and the combined chloroform extracts weredecolorized with activatedcarbon and dried over magnesium sulfate, The volatiles were thenremovedin vacuo, and the residuewas dis tilled, giving 80-85 percent of-3-chloropropylpyridine.

Analysis.-Calcd. for C H NClz N, 9.0. FonndaN, 9.2.

This compound was stored at 20 to prevent polymerization which occursslowly at room temperature. Although a larger quantity may be preparedinone ex periment, attempts to distill more than about g.

at one time resulted in a lower yield and occasionally led to a violent,exothermic polymerization in the distillation flask.

V 3-(y-PYRIDYL)PROPYL DIMETHYLDITHIOCABBAMATE To 10.1 g. .of sodiumdissolved in 500ml. of'dry methanol was added .73 g. of dimethylammonium.di'-' methyldithiocarbamate with stirring. The yellow-togreen solutionwas treated with 45 g. of 'y-3-chloropro pylpyridine, and the reactionmixture was heated with stirring for 6.5 hours. The volatileswereremoved on the steam bath until the volume of solution was about 250ml. This boiling residue was treated with activated carbon and.filtered. The filtrate was cooled, and 250 ml. of waterwas added withcooling. andscratching of the flask with a glass rod. After standing inthe refrigerator overnight, the light brown crystals were filtered andrecrystallized from hexane-chloroform solution, yielding 41.5 g. (60percent.) of 3-(' -pyridyl)propyl dimethyldithiocarbamate which meltedat 60.5-63. Further recrystallization from the same solvent afiorded ananalytical sample, M.P. 62-4". I 7

Analysis.--Calcd. for C H N S C, 55.0, H, 6.7; N,

11.6. Found: C, 55.0; .H,.6.7; N, 11.6. I

v [3 (DIMETHYLDITHIOCARBAMATO)PROPYL] N- METHYLPYRIDINIUM pI'OLUEN'ESULFONATE (COM- POUND 5) To 3.8 g. of 3-( y-pyridyl)propyldimethyldithiocarbamate in 50 ml. of dry ether was added 3.5 g. offreshly distilled methyl p-toluenesulfonate,,and the solution was heatedunder reflux for 3-6 hours. The precipitate was filtered and twicerecrystallized from acetone. The [3 (dim'ethyldithiocarbamato)propyl]N-methylpyridium p-toluenesulfonate thus prepared weighed 4.8 g. (71percent of the theoretical) and melted at 1095-11".

Analysis.-Calcd. for C H N O S C, 53.6; H, 6.1; 'N, 6.6; S, 22.5. Found:C, 53.8; H, 6.0; N, 6.7; S, 22.8.

Compound 1 'Y-PICOLYL DIM'ETHYLDITHIOCARBAMATE By essentially theprocedure described above for 3-( pyridyDpropyl dimethyldithiocarbamate,using 'y-picolyl chloride hydrochloride, 'y-picolyldimethyldithiocarbamate was prepared. Recrystallization of the crudeproduct from chloroform-hexane solvent pair afforded a pure sample, in59 percent yield, which melted at 675-69".

Analysis.-Calcd. for c,H ,N s C, 51.0; H, 5.7; N, 12.7. Found: C, 51.4;H, 6.0; N, 12.6.

7DIMETHYLDITHIOCARBAMATOMETHYL-N-METHYL- PYRIDINIUM p-TOLUENESULFONATE(COMPOUND 1) This compound was prepared in 68 percent yield fromfi-picolyl chloride HCl. It is a yellow oil.

Analysis.Calcd. for cgHuNzsgi C, 51.0; H, 5.7. Found: C, 51.0; H, 5.5.

fl-DIMETHYLD1THIOCARBAMATOMETHYL-N-METHYL- PYRIDINIUM p-TOLUENESULFONATE(COMPOUND 2) This compound was prepared in 87 percentyield as describedfor Compound 5 and melted at 161-1625 after recrystallization frommethanol-acetone.

Analysis.-Calcd. for C17H22N2O3S3: C, 51.3; H, 5.6; N, 7.0. Found: C,51.1; H, 5.9; N, 6.7.

Compound 3 g 3- -PYRIDYL) PROPYL DIETHYLDITHIOCARBAMATE This compoundwas prepared in 71 percent yield from 'y-3-chloropropyl-pyridine andsodium diethyldithiocarbamate. It is a yellow oil, B. 177, which wasfurther purified by chromatography using alumina.

Analysis.--Calcd. for C H N S C, 58.1; H, 7.5; N, 10.4. Found: C,-58.2;H, 7.2; N, 10.0. 'y-[3-(DIETHYLDITHIOCARBAMATO)PROPYL]-N-METH-YLPYRIDINIUM PERCHLORATE (COMPOUND 3) The p-toluenesulfonate salt,prepared in the usual manner, was so hygroscopic that a water solutionof it was treated with an excess of sodium perchlorate in water. Thenon-hydroscopic perchlorate salt (73 percent yield) was filtered andrecrystallized three times from acetone- 7 water solvent pair to afforda puresample of the title compound which melted at l01-2.

Analysis.Calcd. for C H ClN O S N, 7.3; S,

Found: N, 7.2; S, 16.6.

Compound 4 3-fi-PYRIDYLPROPYL DIMETHYLDITHIOCARBAMATEfl-3-Chloropropylpyridine was prepared from 3-pyridine-propanol by themethod described for Compound 5. The p-3-chloropropylpyridine was thenreacted with dimethylammonium dimethyldithiocarbamate as described forCompound 5. However, the product did not crystallize but was isolated asan oil. This brown oil was further purified by chromatography usingalumina as the adsorbent and ether as the solvent. A light yellow oilresulted.

Analysis.-Calcd. for CnHmNgSgZ (2, 55.0; H, 6.7- Found: C, 55.0; H, 7.1.

s [3 (DIMETHYLDITHIOCARBAMATO)PROPYL] N METHYLPYRIDINIUM PERCHLORATE(COMPOUND 4) The p-toluenesulfonate salt, obtained by heating methylp-toluenesulfonate and 3-}9-pyridylpropyl dimethyldithiocarbamatetogether in ether, was treated with a water solution of sodiumperchlorate. was filtered and recrystallized, from acetone-water solventpair and then from acetone giving the title compound,

melting at 75-76.5 in 50 percent yield.

Analysis.Calcd. for C H ClN S O N, 7.9; S, 18.0 Found: N, 7.7; S, 18.3.

The sensitivity increase produced'by the quaternary dithiocarbamates isunexpected for a number of reasons. In the first place, they contain thethiocarbonyl group =C=S which is usually an active source ofdesensitiza- The resulting white solid tion. Furthermore, they are ofrelatively low molecular weight compared to many of the priorsensitizers. Without the quaternary nitrogen atom, these compounds wouldbe incapable of increasing the sensitivity of an already fullychemically sensitized emulsion. Both sulfur atoms in the compound arenecessary for activity, and the reversal of the i gg in the chaindestroystheir activity.

The chemical sensitizing agents and other addenda which we havedescribed may be used in various kinds of photographic emulsions. Inaddition to being useful in non-optically sensitized emulsions they mayalso be used inorthochromatic, panchromatic and X-ray emulsions. Theymay be added to the emulsion before or after any sensitizing dyes whichare used. Various silver salts may be used as the sensitive salt such assilver bromide, silver iodide, silver chloride or mixed silver'halidessuch as silver chlorobromide orsilver bromoiodide. The agents may beused in emulsions intended for color photography, for example, emulsionscontaining color-forming couplers or emulsions to be developed bysolutions containing couplers.

The dispersing agent for the silver halide may be gelatin or othercolloidal material such as collodion, albumin, cellulose derivatives orsynthetic resins.

It will be understood that we contemplate as included within ourinvention all modifications and equivalents falling within. the scope ofthe appended claims.

I What we claim is:

1. A light-sensitive silver halide emulsion sensitized with a quaternarydithiocarbamate having the following composition:

in which R is selected from the class consisting of lower alkyl, hydroxylower alkyl andcarboxy lower alkyl groups, R' represents a lower alkylgroup, J: is an integer from 1 to 3, and X'represents an anion.

2. A light-sensitive silver halide emulsion sensitized with a quaternarydithiocarbamate having the following composition:

in which .1; is an integer from 1 to 3, and X is selected from the groupconsisting of perchlorate and p-toluene sulf onate.

3. A light-sensitive silver halide emulsion sensitized with a quaternarydithiocarbamate having the following composition:

in which 1: is an integer from 1 to 3, and X is selected from the groupconsisting of perchlorate and p-toluene sulfonate.

4. A light-sensitive silver halide emulsion sensitized with a quaternarydithiocarbamate having the following composition:

' i s V anti? -(orn).siiN(cH,)|

References Cited in the file of this patent FOREIGN PATENTS 494,604Canada July 21, 1953

1. A LIGHT-SENSITIVE SILVER HALIDE EMULSION SENSITIZED WITH A QUATERNARYDITHIOCARBAMATE HAVING THE FOLLOWING COMPOSITION: